This invention describes a transverse folder that uses a pre-selected pattern of vacuum ports to hold segments on a roll surface, and air pressure to blow the leading half segment upward before the lead portion is urges into superposed orientation.
The sequence for process steps is different from earlier U.S. Pat. No. 5,904,277.
This invention includes combinations of elements not heretofore described, is derivative of U.S. Pat. No. 5,904,277 and is a continuation of U.S. patent application Ser. No. 09/481,108.
In U.S. Pat. No. 5,904,277, longitudinally folded webs are cut into multi-panel segments by advancing the web through the nip between a roll with knives and a vacuumized roll with anvils. After cutting, the segment is vacuum transported and transferred to the surface of a folding/carrier roll.
Prior art vacuum folding machines like U.S. Pat. No. 1,974,149 of Christman, U.S. Pat. No. 3,689,061 of Nystrand, and U.S. Pat. No. 3,870,292 of Bradley include a knife roll coacting with an anvil roll, and a vacuumized third roll to advance the trailing half panel while the anvil roll lifts the front panel upward before superposing it over the half being advanced by the third roll.
Thus, the prior art requires two rolls to make a singlefold product and an additional third roll to make a double folded product like a dinner napkin.
In this invention, a continuous longitudinally folded web is advanced to, and superposed on, the surface of a folding cylinder which has anvils mounted at pre-selected repeats of the surface rather than being mounted in the separate roll set for cutoff.
In the present invention, the continuous web is held by vacuum ports on opposite sides of the anvil mounted in the cylinder surface while the drum rotates past knives in a coacting adjacent knife roll.
By mounting anvils in the folding cylinder and providing internal air pressure conduits operative through openings in the surface, the functions of cutting, transporting, and folding are all achieved on the same carrier cylinder before the folded product is removed from the processing path.
The separate externally mounted anvil rolls in prior art machines are eliminated by the instant invention.
In singlefold and doublefold prior art folders, inertia of the leading edge portion of an article is reversed in the process of being uplifted and backfolded and is speed limiting.
In the instant invention, both the lead and trailing portions always advance in the same direction and folding does not depend on the instantaneous depletion of vacuum required to release the folded front edge from one roll for advancement on the next.
Folding apparatus with the combination of elements described in this invention overcome the state of the art limits involving extreme weight of wide rolls or rolls with large diameter by decribing lightweight cylinders having internal conduits that are preferably mounted against the inside surface of the drum.
In this invention, use of closed conduits of readily available extruded metal shapes and/or molded plastic results in lower roll weight and less deflection in roll widths over about 80 inches.
With the new combination of elements, wider widths and cylinders with larger diameter and circumference provide space for additional secondary air pressure forces and secondary folding plates to complete a doublefold on the same cylinder.
While matching techniques have improved over the last 60 years since Christman of 1934), practical limits for xe2x80x98rifle drillingxe2x80x99 long conduit holes in solid roills still exist for state of the art folders. The instant invention overcomes these limits.
In another embodiment of the invention, wider machines can process full width webs ex-paper machine to thereby eliminate certain slitting and rewinding operstions currently required to prepare supply rolls for converting.
The inventive combinations that result in larger cylinders permit the beneficial use of two (or more) externally mounted web feed-cutoff units arranged to advance webs each at a speed equal to one half the folder web speed and placement of segments on alternate repeat surfaces of the roll. In this manner, supply rolls last twice as long before supply roll changes and threadup are required compared to conventional practice.
An object of this invention is to provide components and combinations that eliminate limitations of width imposed by limits for drilling long holes in solid rolls.
An object of this invention is to eliminate the vacuum carrier roll as a component in the cutoff unit by mounting anvils in the rticle folding roll.
An object is to provide folding cylinders with internal space for one or more high volume low pressure air flow manifolds or plenums required to blow air radially outward for single and doublefolded products.
An object is to provide wide folders having lightweight cylinders to minimize deflection of roll mounted anvils.
A further object is to provide for conduits made from readily available standard extruded metal shapes.
Another object is to provide for folder arrangements where combination internal air and vacuum conduits can be pre-molded.
A further object is to reduce roll and frame weights, lower bearing and drive transmission duty requirements and reduce motor drive power demand with lighter rolls of this invention.
An object is to define arrangements where a plurality of supply rolls run at speeds lower than the folder to lengthen the time between supply roll changes without reducing folder production speed.
A further object is to describe folder arrangements for processing full width rolls directly from the paper machine without intermediate slitting and rewinding before converting in the folder.
An object is to provide folders with larger circumferential space for mounting two or more cooperating cutoff units to place spaced segments on spaced apart repeat surfaces.
Another object of providing multiple cutoff units described above is to provide stacks of napkins each having different colored napkins in each stack and folded products of different materials.
Other objects may be seen in the ensuing specifications.